Supersonic gas compressor

ABSTRACT

A gas compressor based on the use of a driven rotor having a compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which compresses inlet gas against a stationary sidewall. In using this method to compress inlet gas, the supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdyanamic flow path formed between the rim of the rotor, the strakes, and a stationary external housing. Part load efficiency is enhanced by the use of a pre-swirl compressor, and using a bypass stream to bleed a portion of the intermediate pressure gas after passing through the pre-swirl compressor back to the inlet of the pre-swirl compressor. Inlet guide vanes to the compression ramp enhance overall efficiency.

RELATED PATENT APPLICATIONS

[0001] This application is based on U.S. Provisional Patent ApplicationSerial No. 60/414,793, entitled SUPERSONIC GAS COMPRESSOR, filed Sep.26, 2002, assigned of record on Mar. 28, 2003 at Reel/Frame 013895/0827to Ramgen Power Systems, Inc. of Bellevue, Wash., from which thisapplication claims priority, and the disclosure of which is incorporatedherein in its entirety by this reference.

TECHNICAL FIELD

[0002] This invention relates to a high efficiency, novel gas compressorin which saving of power as well as improved compression performance anddurability are attained by the use of supersonic shock compression ofprocess gas. Compressors of that character are particularly useful forcompression of air, refrigerants, steam, and hydrocarbons.

BACKGROUND

[0003] A continuing demand exists for simple, highly efficient andinexpensive gas compressors as may be useful in a wide variety of gascompression applications. This is because many gas compressionapplications could substantially benefit from incorporating a compressorthat offers a significant efficiency improvement over currently utilizeddesigns. In view of increased energy costs, particularly for both forelectricity and for natural gas, it would be desirable to attainsignificant cost reduction in gas compression. Importantly, it would bequite advantageous to provide a novel compressor which providedimprovements (1) with respect to operating energy costs, (2) withrespect to reduced first cost for the equipment, and (3) with respect toreduced maintenance costs. Fundamentally, particularly from the point ofview of reducing long term energy costs, this would be most effectivelyaccomplished by attaining gas compression at a higher overall cycleefficiency than is currently known or practiced industrially. Thus, theimportant advantages of a new gas compressor design providing thedesirable features of improved efficiency, particularly at part loadoperation, can be readily appreciated.

SUMMARY

[0004] We have now invented a gas compressor based on the use of adriven rotor having a compression ramp traveling at a local supersonicinlet velocity (based on the combination of inlet gas velocity andtangential speed of the ramp) which compresses inlet gas against astationary sidewall. In using this method to compress inlet gas, thesupersonic compressor efficiently achieves high compression ratios whileutilizing a compact, stabilized gasdynamic flow path. Operated atsupersonic speeds, the inlet stabilizes an oblique/normal shock systemin the gasdyanamic flow path formed between the rim of the rotor, thestrakes, and a stationary external housing.

[0005] Efficiency can be further enhanced by using a pre-swirl inletcompressor wheel prior to entry of gas to the supersonic compressionramp. Such pre-swirl inlet compression wheel (a) provides an initialpressure boost over incoming (often ambient atmospheric pressure, in thecase of air compression) gas pressure, and (b) energizes inlet gas in acounterswirling direction to impart an initial velocity vector on theinlet gas so as to increase apparent mach number when the inlet gas isingested by the supersonic compression ramp.

[0006] By use of a gas bypass valve arrangement, the low pressurecompressed gas output (i.e., mass flow rate) from the pre-swirlcompressor unit can be turned down as necessary while maintaining highrotating velocity (utilizing a fixed shaft speed, i.e., constantrotating velocity where necessary or desirable), such as is necessarywhen utilizing constant speed compressor drive apparatus, whilemaintaining minimal output loads. Moreover, this technique allowsmaintenance of relatively high efficiency compression with good turndown capability, since the supersonic compressor wheel continues tooperate at an efficient high speed condition.

[0007] The structural and functional elements incorporated into thisnovel compressor design overcomes significant and serious problems whichhave plagued earlier attempts at supersonic compression of gases inindustrial applications. First, at the Mach numbers at which my deviceoperates (in the range from about Mach 1.5 or lower to about Mach 4.0),the design minimizes aerodynamic drag. This is accomplished by bothcareful design of the shock geometry, as related to the rotatingcompression ramp and the stationary wall, as well as by effective use ofa boundary layer control and drag reduction technique. Thus, the designminimizes parasitic losses to the compression cycle due to the dragresulting simply from rotational movement of the rotor. This isimportant commercially because it enables a gas compressor to avoidlarge parasitic losses that undesirably consume energy and reduceoverall efficiency.

[0008] Also, more fundamentally, this compressor design can develop highcompression ratios with very few aerodynamic leading edges. Theindividual leading edges of the thousands of rotor and stator blades ina conventional high pressure ratio compressor, especially as utilized inthe gas turbine industry, contribute to the vast majority of the viscousdrag loss of such systems. However, in that the design of the novel gascompressor disclosed herein utilizes, in one embodiment, less than fiveindividual aerodynamic leading edges subjected to stagnation pressure,viscous losses are significantly reduced, compared to conventional gascompression units heretofore known or utilized. As a result, the novelcompressor disclosed and claimed herein has the potential to be up toten percentage points more efficient than a conventional gas turbinecompressor, when compared at competing compression ratios in the rangefrom about ten to one (10:1) to about thirty to one (30:1).

[0009] Second, the selection of materials and the mechanical design ofrotating components avoids use of excessive quantities or weights ofmaterials (a vast improvement over large rotating mass bladedcentrifugal compressor designs). Yet, the design provides the necessarystrength, particularly tensile strength where needed in the rotor,commensurate with the centrifugal forces acting on the extremely highspeed rotating components.

[0010] Third, the design provides for effective mechanical separation ofthe low pressure incoming gas from the exiting high pressure gases,while allowing gas compression operation along a circumferentialpathway.

[0011] This novel design enables the use of lightweight components inthe gas compression pathway. To solve the above mentioned problems, wehave now developed compressor design(s) which overcome the problemsinherent in the heretofore known apparatus and methods known to me whichhave been proposed for the application of supersonic gas compression inindustrial applications. Of primary importance, we have now developed alow drag rotor which has one or more gas compression ramps mounted atthe distal edge thereof. A number N of peripherally, preferablypartially helically extending strakes S partition the entering gas flowsequentially to the inlet to a first one of the one or more gascompression ramps, and then to a second one of the one or more gascompression ramps, and so on to an Nth one of the one or more gascompression ramps. Each of the strakes S has an upstream or inlet sideand a downstream or outlet side. For rotor balance and gas compressionefficiency purposes, in one embodiment the number X of gas compressionramps R and the number of strakes N are the same positive integernumber, and in such embodiment, N and X is at least equal to two. In anembodiment shown herein, the number of strakes N and the number X of gascompression ramps R are both equal to three. The compressed gasesexiting from each of the one or more gas compression ramps iseffectively prevented from “short circuiting” or returning to the inletside of subsequent gas compression ramps by the strakes S. Morefundamentally, the strakes S act as a large screw compressor fan or pumpto move compressed gases along with each turn of the rotor.

[0012] To accommodate the specific strength requirements of high speedrotating service, various embodiments for an acceptable high strengthrotor are feasible. In one embodiment, the rotor section may comprise acarbon fiber disc. In another, it may comprise a high strength steelhub. In each case, the gas compression ramps and strakes S may beintegrally provided, or rim segments and gas compression modules may bereleasably and replaceably affixed to the rotor.

[0013] Attached at the radial edge of the rotor are one or more of theat least one gas compression ramps. The gas compression ramps aresituated so as to engage and to compress that portion of the enteringgas stream which is impinged by the gas compression ramp upon itsrotation, which in one embodiment, is about the aforementioned driveshaft. The compressed gases escape rearwardly from the gas compressionramp, and decelerate and expands outwardly into a gas expansion diffuserspace or volute, prior to entering a compressed gas outlet nozzle.

[0014] Finally, many variations in the gas flow configuration and inprovision of the inlet gas preswirl compression, and in providing outletgas passageways, may be made by those skilled in the art withoutdeparting from the teachings hereof. Finally, in addition to theforegoing, my gas compressor is simple, durable, and relativelyinexpensive to manufacture and to maintain.

BRIEF DESCRIPTION OF THE DRAWING

[0015] In order to enable the reader to attain a more completeappreciation of the invention, and of the novel features and theadvantages thereof, attention is directed to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

[0016]FIG. 1 provides a partially cut away perspective view of a gascompressor, showing the use of a two supersonic gas compressor wheelsmounted on a common shaft, and with an integrally mounted, directlydriven centrifugal inlet pre-swirl gas impeller wheel mounted in eachinlet gas stream to compress the inlet low pressure gas from a gassource to an intermediate pressure before feed to each of the supersonicgas compressors.

[0017]FIG. 2 provides a perspective view of a rotor for one of thesupersonic gas compressors, and in particular, illustrating the gascompression ramp provided with the rotor, the helical strakes, and bleedports for controlling the boundary layer flow on the gas compressionramp.

[0018]FIG. 3 is a perspective view providing a close up of thecompression ramp portion on a rotor, showing bleed ports foraccommodating bleed of boundary layer gas at two positions on the gascompression ramp, as well as showing outlets for each bleed port intothe rotor wheel space.

[0019]FIG. 4 illustrates a circumferential view of the gas flow pathinto and out of the rotating shock compressor wheel, without an inflowpre-swirl feature, in that the inlet guide vanes function only as a flowstraightener imparting no pre-swirl into the flow before it is ingestedby the shock compression ramp on the rotor; this figure also illustratesthe use of a radial diffuser downstream of the discharge side of therotating shock compression ramp.

[0020]FIG. 5 illustrates a circumferential view of the gas flow pathinto and out of the rotating shock compressor wheel, similar to the viewjust provided in FIG. 4, but now providing illustrating the use of aninlet guide vane array that imparts pre-swirl into the gas flow prior toentry into the shock compression ramp on the rotor; this figures alsoillustrates the use of a stationary diffusion cascade that achieves flowexpansion largely in the axial direction.

[0021]FIG. 6 provides a comparison of various prior art compressionefficiencies, in terms of total pressure ratio, based on three differenttypes of inlets utilized in supersonic flight applications, namely,normal shock compression, external shock compression, and mixedcompression, to enable the reader to appreciate the advantages providedby integrating the features of external and mixed compression inlets inthe compressor design disclosed and claimed herein; note that a smallillustration of the shock pattern is provided for each type of inlet forwhich data is provided.

[0022]FIG. 7 provides an overview of comparative isentropic compressionefficiencies for different types of compressors as a function ofnon-dimensional specific speed, indicating how the novel supersonic gascompressor disclosed herein can out perform other types of compressorsfor a certain range of specific speeds.

[0023]FIG. 8 provides an overview of comparative isentropic compressionefficiencies for different types of compressors as a function ofnon-dimensional specific speed, and also indicates how the novelsupersonic gas compressor disclosed herein can out perform other typesof compressors for a certain range of specific speeds.

[0024]FIG. 9 provides a partial cross-sectional view of one embodimentfor a novel supersonic gas compressor, and further illustrates, from aprocess flow diagram point of view, the use of intermediate gas bypasswhich enables provision of variable inlet mass flow to the supersoniccompression ramp on a constant speed rotor, and which incidentally alsoshows the close fitting relationship of the rotor strakes with theinterior surface of the stationary peripheral wall against which gascompression occurs, and one position of strakes as the rotor turns aboutits axis of rotation.

[0025] The foregoing figures, being merely exemplary, contain variouselements that may be present or omitted from actual implementationsdepending upon the circumstances. An attempt has been made to draw thefigures in a way that illustrates at least those elements that aresignificant for an understanding of the various embodiments and aspectsof the invention. However, various other elements of the supersonic gascompressor, especially as applied for different variations of thefunctional components illustrated, embodiments, may be utilized in orderto provide a robust supersonic gas compression unit still within theoverall teachings of the present invention, and the legal equivalentsthereof.

DETAILED DESCRIPTION

[0026] Referring now to the drawing, FIG. 1 depicts a partial cut-awayperspective view of my novel supersonic gas compression apparatus 20.Major components shown in this FIG. 1 include a stationary housing orcase 22 having first 24 and second 26 inlets for supply of low pressuregas to be compressed, and a high pressure compressed gas outlet nozzle28. In this dual unit design, a first rotor 30 and a second rotor 32 areprovided, each having a central axis defined along centerline 34, hereshown defined by common shaft 36, and adapted for rotary motiontherewith, in case 22. Each one of the first 30 and second 32 rotorsextends radially outward from its central axis to an outer surfaceportion 38, and further to an outer extremity 40 on the strakes S. Oneach one of first 30 and second 32 rotors, one or more supersonic shockcompression ramps R are provided. Each one of the supersonic shockcompression ramps R forms a feature on the outer surface portion 38 ofits respective first 30 or second 32 rotor. Within housing 22, a firstcircumferential stationary interior peripheral wall 42 is providedradially outward from first rotor 30. Likewise a second circumferentialstationary interior peripheral wall 44 is provided radially outward fromsecond rotor 32. Each one of the stationary peripheral walls 42 and 44are positioned radially outward from the central axis defined bycenterline 34, and are positioned very slightly radially outward fromthe outer extremity 40 of first 30 and second 32 rotors, respectively.Each one of the first and second stationary peripheral walls 42 and 44have an interior surface portion 52 and 54, respectively. Each one ofthe one or more supersonic shock compression ramps R cooperates with theinterior surface portion 52 and 54 of one of the stationary peripheralwalls 42 or 44 to compress gas therebetween.

[0027] One or more helical strakes S are provided adjacent each one ofthe one or more supersonic compression ramps R. An outwardly extendingwall portion S_(W) of each of the one or more strakes S extends outwardfrom at least a portion of the outer surface portion 38 of itsrespective rotor 30 or 32 along a height HH (see FIG. 9) to a pointadjacent the respective interior surface portion 52 or 54 of theperipheral wall 42 or 44. The strakes S effectively separate the lowpressure inlet gas from high pressure compressed gas downstream of eachone of the supersonic gas compression ramps R. Strakes S are, in theembodiment illustrated by the circumferential flow paths depicted inFIGS. 4 and 5, provided in a helical structure extending substantiallyradially outward from the outer surface portion 38 of its respectiverotor 30 or 32. As shown in FIGS. 4 and 5, the number of the one or morehelical strakes S is N, and the number of the one or more supersonic gascompression ramps R is X, and the number N of strakes S is equal to thenumber X of compression ramps R. The strakes S₁ through S_(N) partitionentering gas so that the gas flows to the respective gas compressionramp R then incident to the inlet area of the gas compressor. As can beappreciated from FIG. 9, the preferably helical strakes S₁, S₂, and S₃are thin walled, with about 0.15″ width (axially) at the root, and about0.10″ width at the tip. With the design illustrated herein, it isbelieved that leakage of gases will be minimal.

[0028] For rotor 30 or 32 balance purposes, we prefer that the number Xof gas compression ramps R and the number N of strakes S be the samepositive integer number, and that N and X each be at least equal to two.In one embodiment, N and X are equal to three as illustrated herein. Thestrakes S₁ through SN allow feed of gas to each gas compression ramp Rwithout appreciable bypass of the compressed high pressure gas to theentering low pressure gas. That is, the compressed gas is effectivelyprevented by the arrangement of strakes S from “short circuiting” andthus avoids appreciable efficiency losses. This strake feature can bebetter appreciated by evaluating the details shown in FIG. 9, wherestrakes S₁ and S₂ revolves in close proximity to the interior wallsurface 52. The strakes S₁ and S₂ have a localized height HS1 and alocalized height HS₂, respectively, which extends to a tip end TS₁ andTS₂ respectively, that is designed for rotation very near to theinterior peripheral wall surface of housing 22, to allow for fitting inclose proximity to the tip end TS, or TS₂ with that wall.

[0029] As seen in FIG. 3, in each of the gas compression ramps R, theinlet gas stream is compressed at apparent supersonic velocity, tocreate an oblique/normal shock structure between the respective gascompression ramp and the adjacent peripheral wall. Each of the one ormore gas compression ramps R has an outwardly sloping gas compressionramp face 60. The face 60 has a base 62 which is located adjacent theintersection of the outwardly sloping face 60 and the outer surfaceportion 38 of the respective rotor 30 or 32. The face 60 and the outersurface 38 of rotors 30 and 32 intersect at a preselected angle alpha aof from about one (1) degree to about fifteen (15) degrees, which anglealpha a will vary based on the design Mach number and gas properties,such as temperature and density. The gas compression ramps R alsoinclude a throat 70, and downstream thereof, an inwardly sloping gasdeceleration section 72. The deceleration-transition section 72 isprovided to step-down to the outer surface 38 of the rotor 30 or 32.

[0030] For improving efficiency, each of the one or more gas compressionramps R has one or more boundary layer bleed ports B. In theconfiguration illustrated in FIG. 3, at least one of the one or moreboundary bleed ports B is located at the base 62 of the gas compressionramp R. As depicted, a pair of shovel-scoop shaped cutouts B₁ are shown,each having a generally parallelepiped sidewall 64 configuration. Bleedair enters structures B₁ as indicated by reference arrows 76 in FIG. 3.Also, as shown in FIG. 3, at least one of the one or more boundary bleedports B₂ are located on the face 60 of the gas compression ramp R. Bleedair enters structures B₂ as indicated by reference arrows 78 in FIG. 3.As depicted in FIG. 3, each one of the gas compression ramps R furthercomprise a bleed air receiving chamber 80, each of which is configuredfor effectively containing therein, for ejection therefrom, bleed airprovided thereto, as indicated by exit bleed air reference arrows 84 inFIG. 3.

[0031] As depicted in FIG. 1, downstream of each of first 30 and second32 rotors is a first 90 and second 92 high pressure outlet,respectively, each configured to receive and pass therethrough highpressure outlet gas resulting from compression of gas by the one or moregas compression ramps R on the respective rotor 30 or 32. One or morecombined high pressure gas outlet nozzles 28 can be utilized, as shownin FIG. 1, to receive the combined output from the first and second highpressure outlets 90 and 92 from rotors 30 and 32.

[0032] For improved efficiency and operational flexibility, thecompressor 20 may be designed to further include a first inlet casing100 and a second inlet casing 102 having therein, respectively, first104 and second 106 pre-swirl impellers. These pre-swirl impellers 104and 106 are located intermediate the low pressure gas inlets 24 and 26,and their respective first 30 or second 32 rotors. Each of the pre-swirlimpellers 104 and 106 are configured for compressing the low pressureinlet gas LP to provide an intermediate pressure gas stream IP at apressure intermediate the pressure of the low pressure inlet gas LP andthe high pressure outlet gas HP, as noted in FIG. 9. In one applicationfor the apparatus depicted, air at ambient atmospheric conditions of14.7 psig is compressed to about 20 psig by the pre-swirl impellers 104and 106. However, such pre-swirl impellers can be configured to providea compression ratio of up to about 2:1. More broadly, the pre-swirlimpellers can be configured to provide a compression ratio from about1.3:1 to about 2:1.

[0033] Also, for improving efficiency, the gas compressor 20 can beprovided in a configuration wherein, downstream of the pre-swirlimpellers 104 and 106, but upstream of the one or more gas compressionramps R on the respective rotors 30 and 32, a plurality of inlet guidevanes, are provided, a first set 110 or 110′ before first rotor 30 and asecond set 112 or 112′ before second rotor 32. The inlet guide vanes110′ and 112′ as illustrated in FIG. 5 impart a spin on gas passingtherethrough so as to increase the apparent inflow velocity of gasentering the one or more gas compression ramps R. Additionally, suchinlet guide vanes 110′ and 112′ assist in directing incoming gas in atrajectory which more closely matches gas flow path through the ramps R,to allow gas entering the one or more gas compression ramps to be atapproximately the same angle as the angle of offset, to minimize inletlosses.

[0034] In one embodiment, as illustrated, the pre-swirl impellers 104and 106 can be provided in the form of a centrifugal compressor wheel.As illustrated in FIG. 1, pre-swirl impellers 104 and 106 can be mountedon a common shaft 36 with the rotor 30 and 32. It is possible tocustomize the design of the pre-swirl impeller and the inlet guide vaneset to result in a supersonic gas compression ramp inlet inflowcondition with the same pre-swirl velocity or Mach number but asuper-atmospheric pressure. Since the supersonic compression ramp inletbasically multiples the pressure based on the inflow pressure and Machnumber, a small amount of supercharging at the pre-swirl impellers canresult in a significant increase in cycle compression ratio.

[0035] In FIG. 4, a circumferential view of the gas flow path into andout of the rotating shock compressor wheel is provided, where theconfiguration is developed without an inflow pre-swirl feature, in thatthe inlet guide vanes 110 and 112 function only as a flow straightener,imparting no pre-swirl into the flow before it is ingested by the shockcompression ramp R on the rotor 30 or 32. Note that this figure alsoillustrates the use of a radial diffuser having a plurality of radialdiffuser blades 116, downstream of the discharge side of the rotatingshock compression ramp R, to then deflect compressed high pressure gasHP outward toward outlet (90 or 92, shown in FIG. 1) in the direction ofreference arrows 117.

[0036]FIG. 5 illustrates a circumferential view of the gas flow pathinto and out of the rotating shock compressor R on rotor wheels 30 and32, similar to the view just provided in FIG. 4, but now furtherillustrating the use of an array of inlet guide vanes 110′ and 112′ thatimparts pre-swirl into the gas flow prior to entry into the shockcompression ramp R on the rotor 30 or 32. Note that this figure alsoillustrates the use of a stationary diffusion cascade blades 121 thatachieves flow expansion largely in the axial direction, as shown byreference arrows 123.

[0037] With (or without) the aid of pre-swirl impellers 104 and 106, itis important that the apparent velocity of gas entering the one or moregas compression ramps R is in excess of Mach 1, so that the efficiencyof supersonic shock compression can be exploited. However, to increaseefficiency, it would be desirable that the apparent velocity of gasentering the one or more gas compression ramps R be in excess of Mach 2.More broadly, the apparent velocity of gas entering the one or more gascompression ramps R can currently practically be between about Mach 1.5and Mach 3.5, although wider ranges are certainly possible within theteachings hereof.

[0038] As depicted in FIG. 9, another aspect of the current invention isthe provision, where desirable for maintaining relatively highefficiency at reduced mass flows from design maximum flow rate of thecompressor 20, to further include, adjacent the outlet of the pre-swirlimpeller 104 or 106, an outlet 120 for intermediate pressure gas, and abypass line 122 between the intermediate outlet 120 and the gas inlet24, so that the bypass line 122 is configured to route a portion of thegas at the intermediate pressure to the gas inlet 24. In thisconfiguration, it is advantageous to utilize gas flow regulating valve130. The valve 130 is configured to vary the rate of passage ofintermediate pressure gas therethrough, so as to in turn vary the amountof intermediate pressure gas entering the one or more gas compressionramps R on rotor 30. From the other discussion herein, it should beclear to one of ordinary skill in the art and to whom this specificationis directed that a duplicate valve 130 may be provided with respect to asecond rotor 32 for achieving equivalent results (i.e., mirror image ofthe portion shown in FIG. 9). In one embodiment, valve 130 is adjustableat any preselected flow rate from (a) a closed position, wherein thevalve 130 seals the bypass line 122, so that as a result substantiallyno intermediate pressure gas escapes to the gas inlet, and (b) an openposition, wherein the valve 130 allows fluid communication between thepre-swirl impeller outlet 120 and the gas inlet, or (c) a preselectedposition between the closed position and the open position.

[0039] The compressor 20 provides an ideal apparatus for the compressionof various gases, including (a) air, (b) refrigerant, (c) steam, and (d)hydrocarbons. In various applications, it has been calculated thatcompressor 20 is capable of providing compression of a selected gas atan isentropic efficiency in excess of ninety (90) percent, as isgraphically illustrated in FIGS. 7 and 8. The compressor 20 operatesmost efficiently at a non-dimensional specific speed from about 60 toabout 120. As further depicted in FIG. 8, the compressor 20 is capableof compressing a selected gas at an isentropic efficiency in excess ofninety five percent.

[0040] For assuring operation at high rotational speed, to achieve highapparent Mach number at the inlet of each of the one or more gascompression ramps R, a high strength rotor 30 or 32 is provided. In oneembodiment, such rotors include a high strength central disc. Asillustrated in FIG. 2, such rotors, and in particular a central discportion 140, may include a tapered portion 142, at least in part, i.e.,that is thinner at increasing radial distance from the center ofrotation. To increase aerodynamic efficiency, at least a portion of suchrotor can be confined within a close fitting housing having a minimaldistance D between an outer surface of the rotor and an inner surface ofthe close fitting housing, so as to minimize aerodynamic drag on therotor. These aspects of the design of such compressors 20 can be seen inFIG. 1.

[0041] The compressor 20 disclosed herein allows practice of uniquemethods of compressing gases. Practice of such methods involvesproviding one or more gas compression ramps on a rotor which isrotatably secured for high speed rotary motion with respect tostationary housing having an inner surface. Each of the one or more gascompression ramps is provided with an inlet, low pressure gas stream.The low pressure gas is compressed between one of the one or more gascompression ramps and the inner surface of the stationary housing whichis located circumferentially about the rotor, to generate a highpressure gas therefrom. To achieve gas compression, and to avoid bypassof the compressed gas back to the entering low pressure gas stream, oneor more helical, substantially radially extending strakes are providedalong the periphery of the rotor. Each on of the one or more strakes Sis provided adjacent to one of the one or more gas compression ramps R.At least a portion of each of the one or more strakes S extends outwardfrom at least a portion of an outer surface portion of the rotor to apoint adjacent to the inner surface of the stationary housing. The rotoris driven by application of mechanical power to an input shaftoperatively connected to the rotor, and thus to each of the one or moregas compression ramps. In one embodiment, the apparent inlet velocity ofthe one or more gas compression ramps, i.e., the approach speed betweenincoming gas and the opposing motion of a selected gas compression rampR, is at least Mach 1.5. More broadly, the apparent inlet velocity ofthe one or more gas compression ramps is between Mach 1.5 and Mach 4. Atthe design point in one embodiment, the apparent inlet velocity of saidgas compression ramps is approximately Mach 3.5.

[0042] This method of gas compression allows high efficiency compressionof a variety of commonly compressed gases, including (a) air, (b) steam,(c) refrigerant, and (d) hydrocarbons. Some important applicationsinclude compression of air, natural gas, refrigerants in refrigerationand air conditioning, applications, and steam in various services.

[0043] Overall, the designs incorporated into compressor 20 provide forminimizing aerodynamic drag, by minimizing the number of leading edgesurfaces subjected to stagnation pressure within the compressor. In oneembodiment, as illustrated herein, the number of leading edge surfacessubjected to stagnation pressure is less than five. And, each of the oneor more gas compression ramps are circumferentially spaced equally apartso as to engage a supplied gas stream substantially free of turbulencefrom the previous passage through a given circumferential location ofany one said one or more gas compression ramps. The cross sectionalareas of each of the one or more gas compression ramps can be sized andshaped to provide a desired compression ratio. Further, the helicalstrakes can be offset at a preselected angle delta, and wherein theangle of offset matches the angle of offset of each one of the one ormore gas compression ramps, and wherein so that the angles match toallow gas entering the one or more gas compression ramps to be atapproximately the same angle as the angle of offset, to minimize inletlosses.

[0044] The rotors 30 and 32 are rotatably secured in an operatingposition by a fixed support stationary housing or casing 22 in a mannersuitable for extremely high speed operation of the rotors 30 and 32,such as rotation rates in the range of 10,000 to 20,000 rpm, or even upto 55,000 rpm, or higher. In this regard, bearing assemblies mustprovide adequate bearing support for high speed rotation and thrust,with minimum friction, while also sealing the operating cavity, so as toenable provision of a vacuum environment adjacent the rotor disc, tominimize drag. The detailed bearing and lubrication systems may beprovided by any convenient means by those knowledgeable in high speedrotating machinery, and need not be further discussed herein. However,note that in the embodiment shown in FIG. 1, with “back-to-back”mounting of opposing pre-swirl impellers and opposing rotor discs, thethrust vectors created during compression are effectively eliminatedsince they are basically created in equal but opposite directions by theopposing rotors and pre-swirl impellers.

[0045] It is to be appreciated that the various aspects and embodimentsof a supersonic gas compressor, and the method of operating such devicesas described herein are an important improvement in the state of theart. The novel supersonic gas compressor is simple, robust, reliable,and useful for work in various gas compression applications. Althoughonly a few exemplary embodiments have been described in detail, variousdetails are sufficiently set forth in the drawings and in thespecification provided herein to enable one of ordinary skill in the artto make and use the invention(s), which need not be further described byadditional writing in this detailed description.

[0046] Importantly, the aspects and embodiments described and claimedherein may be modified from those shown without materially departingfrom the novel teachings and advantages provided by this invention, andmay be embodied in other specific forms without departing from thespirit or essential characteristics thereof. Therefore, the embodimentspresented herein are to be considered in all respects as illustrativeand not restrictive. As such, this disclosure is intended to cover thestructures described herein and not only structural equivalents thereof,but also equivalent structures. Numerous modifications and variationsare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, theinvention(s) may be practiced otherwise than as specifically describedherein. Thus, the scope of the invention(s), as set forth in theappended claims, and as indicated by the drawing and by the foregoingdescription, is intended to include variations from the embodimentsprovided which are nevertheless described by the broad interpretationand range properly afforded to the plain meaning of the claims set forthbelow.

What is claimed is:
 1. A gas compressor, said compressor comprising: (a)an inlet for supply of gas to be compressed; (b) a rotor, said rotorhaving a central axis and adapted for rotary motion thereabout, saidrotor extending radially outward from said central axis to an outersurface portion having an outer extremity; (c) one or more supersonicshock compression ramps, each one of said supersonic shock compressionramps forming a features on said outer surface portion of said rotor;(d) a stationary peripheral wall, said stationary peripheral wall (i)positioned radially outward from said central axis, and (ii) positionedvery slightly radially outward from said outer extremity of said rotor;and (iii) having an interior surface portion; (e) said one or moresupersonic shock compression ramps and said stationary peripheral wallcooperating to compress said gas therebetween; (f) one or more strakes,each of said one or more strakes provided adjacent to one of said ormore supersonic compression ramps, and at least a portion of each ofsaid one or more strakes extending outward from at least a portion ofsaid outer surface portion of said rotor to a point adjacent saidinterior surface portion of said peripheral wall; (g) whereby said oneor more strakes effectively separate said inlet gas from compressed gasdownstream of each one of said supersonic gas compression ramps.
 2. Theapparatus as set forth in claim 1, wherein each of said one or morestrakes comprises a helical structure extending substantially radiallyfrom said outer surface portion of said rotor.
 3. The apparatus as setforth in claim 2, wherein the number of said one or more helical strakesis N, and the number of said one or more supersonic gas compressionramps is X, and wherein N and X are equal.
 4. The apparatus as set forthin claim 1 or in claim 2, wherein each of said one or more gascompression ramps comprises a outwardly sloping gas compression rampface, said face having a base, said base located adjacent theintersection of said outwardly sloping face and said outer surfaceportion of said rotor.
 5. The apparatus as set forth in claim 1, orclaim 2, or claim 4, wherein each of said one or more gas compressionramps further comprise one or more boundary layer bleed ports.
 6. Theapparatus as set forth in claim 5, wherein at least one of said one ormore boundary bleed ports is located at said base of said gascompression ramps.
 7. The apparatus as set forth in claim 5, wherein atleast one of said one or more boundary bleed ports is located on saidface of said gas compression ramp.
 8. The apparatus as set forth inclaim 4, wherein said face and said outer surface of said rotorintersect at an angle alpha a from about one degree to about fifteendegrees.
 9. The apparatus as set forth in claim 1, wherein said gascompression ramps further comprise (a) a throat, and (b) an inwardlysloping gas deceleration ramp.
 10. The apparatus as set forth in claim5, wherein each of said gas compression ramps further comprise a bleedair receiving chamber, and wherein each of said bleed air receivingchambers effectively contains therein, for ejection therefrom, bleed airprovided thereto.
 11. The apparatus as set forth in claim 1, furthercomprising an outlet, said outlet configured to receive and passtherethrough high pressure outlet gas after resulting from compressionof gas by said one or more gas compression ramps on said rotor.
 12. Theapparatus as set forth in claim 11, further comprising an inlet casingcontaining therein a pre-swirl impeller, said pre-swirl impeller locatedintermediate said gas inlet and said rotor, said pre-swirl impellerconfigured for compressing said inlet gas to a pressure intermediate thepressure of said inlet gas and said outlet gas.
 13. The apparatus as setforth in claim 12, wherein said pre-swirl impeller is configured toprovide a compression ratio of up to about 2:1.
 14. The apparatus as setforth in claim 12, wherein said pre-swirl impeller is configured toprovide a compression ratio from about 1.3:1 to about 2:1.
 15. Theapparatus as set forth in claim 12, further comprising, downstream ofsaid pre-swirl impeller and upstream of said one or more gas compressionramps on said rotor, a plurality of inlet guide vanes, said inlet guidevanes imparting spin on gas passing therethrough so as to increase theapparent inflow velocity of gas entering said one or more gascompression ramps.
 16. The apparatus as set forth in claim 15, whereinsaid pre-swirl impeller comprises a centrifugal compressor.
 17. Theapparatus as set forth in claim 16, wherein said pre-swirl impeller ismounted on a common shaft with said rotor.
 18. The apparatus as setforth in claim 15, wherein the apparent velocity of gas entering saidone or more gas compression ramps is in excess of Mach
 1. 19. Theapparatus as set forth in claim 15, wherein the apparent velocity of gasentering said one or more gas compression ramps is in excess of Mach 2.20. The apparatus as set forth in claim 15, wherein the apparentvelocity of gas entering said one or more gas compression ramps isbetween about Mach 1.5 and Mach 3.5.
 21. The apparatus as set forth inclaim 12, or in claim 20, wherein said pre-swirl impeller has an outletfor intermediate pressure gas, and wherein said apparatus furthercomprises a bypass line between said intermediate outlet and said gasinlet, said bypass line configured to route a portion of said gas atsaid intermediate pressure to said inlet.
 22. The apparatus as set forthin claim 21, further comprising a gas flow regulating valve, said valveconfigured to vary the rate of passage of intermediate gas therethrough,so as to in turn vary the amount of intermediate pressure gas enteringsaid one or more gas compression ramps.
 23. The apparatus as set forthin claim 22, where in said valve is adjustable at any preselected flowrate from (a) a closed position, wherein said valves forms a seal insaid bypass line, so that as a result substantially no intermediatepressure gas escapes to said gas inlet, and (b) an open position,wherein said valve allows fluid communication between said pre-swirlimpeller outlet and said gas inlet, or (c) a preselectd position betweensaid closed position and said open position.
 24. A gas compressor,comprising: (a) a support structure, said support structure comprising(i) a circumferential housing with an inner side surface, and (ii) a gasinlet for receiving low pressure inlet gas; (b) a first drive shaft,said first drive shaft rotatably secured along an axis of rotation withrespect to said support structure; (c) a first rotor, said first rotorrotatably affixed with said first output shaft for rotation with respectto said support structure, said first rotor further comprising a firstcircumferential portion having a first outer surface portion, said firstrotor comprising one or more gas compression ramps, each one of said gascompression ramps comprising a portion integrally provided as part ofsaid circumferential portion of said first rotor, (d) said gascompressor adapted to utilize at least a portion of said inner sidesurface of said first circumferential housing to compress said inlet gasthere against; (e) one or more strakes on said first rotor, wherein oneof said one or more strakes on said first rotor is provided for each ofsaid one or more gas compression ramps, and wherein each of said one ormore strakes on said first rotor extends outward from at least a portionof said circumferential portion of said first rotor to a point adjacentto said inner side surface of said first circumferential housing; and(f) a first high pressure compressed gas outlet.
 25. The apparatus asset forth in claim 24, further comprising: (a) a second rotor, saidsecond rotor rotatably affixed with said first output shaft for rotationwith respect to said support structure, said second rotor furthercomprising a second circumferential portion having a second outersurface portion, said second rotor comprising one or more gascompression ramps, each one of said gas compression ramps comprising aportion integrally provided as part of said circumferential portion ofsaid second rotor, (b) said gas compressor adapted to utilize at least aportion of said inner side surface of said second circumferentialhousing to compress said inlet gas there against; (c) one or morestrakes on said second rotor, wherein one of said one or more strakes onsaid second rotor is provided for each of said one or more gascompression ramps, and wherein each of said one or more strakes on saidsecond rotor extends outward from at least a portion of saidcircumferential portion of said second rotor to a point adjacent to saidinner side surface of said second circumferential housing; and (d) asecond high pressure compressed gas outlet.
 26. The apparatus as setforth in claim 25, wherein said first and second high pressure gasoutlets are in fluid communication with a single high pressure gasoutlet nozzle.
 27. The apparatus as set forth in claim 25, wherein eachof said one or more strakes on said first rotor and on said second rotorcomprises a helical structure extending substantially radially from saidouter surface portion of said first rotor or said second rotor,respectively.
 28. The apparatus as set forth in claim 27, wherein thenumber of said one or more helical strakes on said first rotor or onsaid second rotor is N, and the number of said one or more supersonicgas compression ramps on said first rotor or on said second rotor is X,and wherein N and X are equal.
 29. The apparatus as set forth in claim25, wherein each of said one or more gas compression ramps comprises aoutwardly sloping gas compression ramp face, said face having a base,said base located adjacent the intersection of said outwardly slopingface and said outer surface portion of said first rotor of said secondrotor.
 30. The apparatus as set forth in claim 29 wherein each of saidone or more gas compression ramps further comprise one or more boundarylayer bleed ports.
 31. The apparatus as set forth in claim 30, whereinat least one of said one or more boundary bleed ports is located at saidbase of said gas compression ramps.
 32. The apparatus as set forth inclaim 30, wherein at least one of said one or more boundary bleed portsis located on said face of said gas compression ramp.
 33. The apparatusas set forth in claim 25, wherein each of said gas compression rampsfurther comprise a bleed air receiving chamber, and wherein each of saidbleed air receiving chambers effectively contains therein, for ejectiontherefrom, bleed air provided thereto.
 34. The apparatus as set forth inclaim 25, further comprising a first inlet casing containing therein afirst pre-swirl impeller, said first pre-swirl impeller locatedintermediate said gas inlet and said first rotor, said first pre-swirlimpeller configured for compressing said inlet gas to a pressureintermediate the pressure of said inlet gas and said outlet gas.
 35. Theapparatus as set forth in claim 34, further comprising a second inletcasing containing therein a second pre-swirl impeller, said secondpre-swirl impeller located intermediate said gas inlet and said secondrotor, said second pre-swirl impeller configured for compressing saidinlet gas to a pressure intermediate the pressure of said inlet gas andsaid outlet gas.
 36. The apparatus as set forth in claim 35, whereinsaid first and said second pre-swirl impellers are configured to providea compression ratio of up to about 2:1.
 37. The apparatus as set forthin claim 36, wherein said first and said second pre-swirl impellers areconfigured to provide a compression ratio from about 1.3:1 to about 2:1.38. The apparatus as set forth in claim 35, further comprising,downstream of said first and said second pre-swirl impellers andupstream of said one or more gas compression ramps on said first andsaid second rotors, respectively, a plurality of inlet guide vanes, saidinlet guide vanes imparting spin on gas passing therethrough so as toincrease the apparent inflow velocity of gas entering said one or moregas compression ramps on said first rotor and on said second rotor. 39.The apparatus as set forth in claim 35, wherein said first and saidsecond pre-swirl impellers each comprise a centrifugal compressor. 40.The apparatus as set forth in claim 35, wherein said first and saidsecond pre-swirl impeller is mounted on a common shaft with said firstrotor and with said second rotor.
 41. The apparatus as set forth inclaim 25, wherein the apparent velocity of gas entering said one or moregas compression ramps is in excess of Mach
 1. 42. The apparatus as setforth in claim 25, wherein the apparent velocity of gas entering saidone or more gas compression ramps is in excess of Mach
 2. 43. Theapparatus as set forth in claim 25, wherein the apparent velocity of gasentering said one or more gas compression ramps is between about Mach1.5 and Mach 3.5.
 44. The apparatus as set forth in claim 35, whereinsaid first pre-swirl impeller has a first intermediate outlet, andwherein said apparatus further comprises a first bypass line betweensaid first intermediate outlet and said first gas inlet, said firstbypass line configured to route a portion of said gas at saidintermediate pressure to said first inlet.
 45. The apparatus as setforth in claim 44, wherein said second pre-swirl impeller has a secondintermediate outlet, and wherein said apparatus further comprises asecond bypass line between said second intermediate outlet and saidsecond gas inlet, said second bypass line configured to route a portionof gas at said intermediate pressure to said second inlet.
 46. Theapparatus as set forth in claim 45, further comprising a first and asecond gas flow regulating valve, each one of said first and secondvalves configured to vary the rate of passage of intermediate gasthrerethrough, so as to in turn vary the amount of intermediate pressuregas entering said one or more gas compression ramps on said first rotorand on said second rotor.
 47. The apparatus as set forth in claim 46,where in said valves are adjustable at any preselected flow rate from(a) a closed position, wherein said valves form a seal in said first orin said second bypass line respectively, so that as a resultsubstantially no intermediate pressure gas escapes to said first or saidsecond gas inlets, and (b) an open position, wherein said valves allowfluid communication between said first and said second pre-swirlimpeller outlets and said first and said second gas inlets,respectively, or (c) a preselected position between said closed positionand said open position.
 48. The apparatus as set forth in claim 1, or inclaim 24, wherein said apparatus is configured to compress a gasselected from the group consisting of (a) air, (b) refrigerant, (c)steam, and (d) hydrocarbons.
 49. The apparatus as set forth in claim 1,or in claim 24, wherein said apparatus compresses a selected gas at anisentropic efficiency in excess of ninety (95) percent.
 50. Theapparatus as set forth in claim 1, or in claim 24, wherein saidapparatus compresses a selected gas at an isentropic efficiency inexcess of ninety (90) percent.
 51. The apparatus as set forth in claim50, wherein said apparatus operates at a dimensioned specific speed fromabout 60 to about
 120. 52. The apparatus as set forth in claim 51,wherein said apparatus compresses a selected gas at an isentropicefficiency in excess of ninety five percent.
 53. The apparatus of claim1, or claim 24, wherein said rotor comprises a central disc.
 54. Theapparatus of claim 53, wherein said central disc is tapered, at least inpart.
 55. The apparatus as set forth in claim 1, or in claim 24, whereinat least a portion of said rotor is confined within a close fittinghousing having a minimal distance D between said rotor and said housing,so as to minimize aerodynamic drag on said rotor.
 56. A method ofcompressing gas, comprising: (a) providing one or more gas compressionramps on a rotor which is rotatably secured with respect to stationaryhousing having an inner surface; (b) supplying to each of said one ormore gas compression ramps an inlet gas stream; (c) compressing saidinlet gas stream between said one or more gas compression ramps and saidstationary housing, to generate a high pressure gas therefrom; (d)effectively separating inlet gas from high pressure gas by using one ormore strakes along the periphery of said rotor, each of said one or morestrakes provided adjacent to one of said or more gas compression ramps,and at least a portion of each of said one or more strakes extendingoutward from at least a portion of an outer surface portion of saidrotor to a point adjacent said inner surface of said stationary housing;(e) driving said rotor by an input shaft operatively connected to saidone or more gas compression ramps.
 57. The method as recited in claim56, wherein the apparent inlet velocity of said one or more gascompression ramps is at least Mach 2.5.
 58. The method as recited inclaim 56, wherein the inlet velocity of said one or more gas compressionramps is between Mach 2.5 and Mach
 4. 59. The method as recited in claim56, wherein the apparent inlet velocity of said gas compression ramps isapproximately Mach 3.5.
 60. The method as recited in claim 56, whereinsaid gas is selected from the group consisting of (a) air, (b) steam,(c) refrigerant, and (d) hydrocarbons.
 61. The method as recited inclaim 56, wherein said gas is essentially natural gas.
 62. The method asrecited in claim 56, wherein said gas is air.
 63. The method as recitedin claim 56, wherein said gas comprises a refrigerant.
 64. The method asrecited in claim 56, wherein said gas comprises steam.
 65. The method asrecited in claim 56, further comprising the step of minimizingaerodynamic drag by minimizing the number of leading edge surfacessubjected to stagnation pressure.
 66. The method as recited in claim 65,wherein the number of leading edge surfaces subjected to stagnationpressure is less than five.
 67. The method as recited in claim 65,wherein the number of leading edge surfaces subjected to stagnationpressure is four.
 68. The method as recited in claim 56, wherein each ofsaid one or more gas compression ramps are circumferentially spacedequally apart so as to engage said supplied gas stream substantiallyfree of turbulence from the previous passage through a givencircumferential location of any one said one or more gas compressionramps.
 69. The method as recited in claim 56, wherein the crosssectional areas of each of the one or more gas compression ramps aresized and shaped to provide a desired compression ratio.
 70. The methodas set forth in claim 69, wherein the helical strakes are offset at apreselected angle delta, and wherein the angle of offset matches theangle of offset of each one of said one or more gas compression ramps,and wherein said angles match to allow gas entering the one or more gascompression ramps to be at approximately the same angle as the angle ofoffset, to minimize inlet losses.